Mass spectrometer for simultaneous multiple gas determinations



June 17, 1952 R. CRAWFORD 2,601,097

MASS SPECTROMETER FOR SIMULTANEOUS MULTIPLE GAS DETERMINATIONS Filed July 20, 1949 2 SHEETSSHEET l Fllll FORfPU/VP 64L yawn/7525 191 271110 E. Crawford June 17, 1952 R CRAWFORD 2,601,097

MASS SPECTROMETER FOR SIMULTANEOUS MULTIPLE GAS DETERMINATIONS Filed July 20, 1949 2 SHEETS-SHEET 2 Patented June 17, 1952 UNITED STATES PATENT OFFICE MASS SPECTROMETER FOR SIMULTANEOUS MULTIPLE GAS DETERMINATIONS Arthur R. Crawford, Worthington, Ohio Application July 20, 1949, Serial No. 105,808

This invention relates to improvements in mass spectrometers, having particular reference to a spectrometer especially designed for analyses of individual gases which comprise a body of mixed gases, whereby to disclose continuously variations in the relative abundance or concentration of such individual gases.

There exists at the present time a need for a continuously recording gas analyzer in the field of respiratory research, as an adjunct in diagnosing various lung disorders. It is, therefore, an object of the present invention to provide gasanalyzing apparatus for disclosing continuously by tracings on a motion picture film or the like the component gases present in the exhaled breath, including variations in concentration of the individual gases present when a given test is being conducted.

It is another object of the invention to provide a mass spectrometer so constructed as to form an instantaneously and continuously operating analyzer for effecting qualitative and quantitative determinations of the individual components present in a body of mixed gases.

In providing for the continuous analysis of the composition of human breath, a primary problem has been to minimize the time lag of the ap--. paratus, that is, the interval of time occurring between an actual change in the concentration of an individual gas and the notation of such I change on aregistering or recording device therefor. In a breath analyzer, it is essential to render said time lag as small as possible, since the average human subject exhales and inhales once every six seconds. The usual mass spectrometer as heretofore constructed has a time lag of approximately twenty seconds or more in the interval occurring between the change in gas concentration'and recordation of such change.

It is, therefore, a further object of the present invention to provide a mass spectrometer in which the element of time lag is reduced to a negligible degree.

A further object is to provide an analyzer capable of handling simultaneously the three main components of the breath, namely, carbon dioxide, nitrogen, and oxygen, so that such components may be recorded simultaneously, whereby changes in concentration of any one of the three gases can be seen with respect to the others at any given instant while a test is being conducted.

For a further understanding of the invention,

referenceis to be had to the following description I 2 Claims. (Cl. 250-413) view taken through the needle valve assembly of the apparatus; I

Fig. 3 is an enlarged detail sectional view of the nozzle tip region of the valve on the line 3-8 of Fig. 2;

Fig. 4 is a similar view taken through the tip of the sample-introducing nozzle.

Referring more particularly to the drawings, there has been disclosed at I the needle valve assembly of my improved spectrometer. The gas sample to be analyzed is drawn into the valve through an open tube indicated at 2. This tube is inserted into a body member 4 so that the gas sample to be analyzed is drawn into a longitudinally extending passage 5 provided in said body member. At one end, the body member is formed with a collar 6 which engages with a gasket 1, the latter being arranged between the outer face of the collar 6 and an adjacent face of an orifice member 8.

The member 8 comprises a circular head plate 9 which is detachably secured to the upper end of a spectrometer tube T. The plate 9 is formed with an axial extension I0 which is externally threaded at its outer end for the reception of an internally threaded sleeve II, the latter being formed with an inturned fiange I2 which cooperates with the collar 6 of the body member 4 for the purpose of clamping said body member to the orifice member.

The extension Ill terminates in a nozzle tip I3 having a tapered outer end I4, said tip being formed with a longitudinally extending axial passage I5 which communicates with a pair of larger longitudinally extending bores IE provided in the extension III, the bores I6 being in communication with the interior of the tube T. The extreme outer end of the tip, as shown in Fig. 4, is countersunk as at 11 to facilitate gas collection therein. The tip I3 is spaced from the walls of the passage 5 provided in the body member 4, so that the main body of the gas undergoing sampling or testing may travel through the passage 5 Without diversion and find exit through a pipe line [8 leading to a suction-producing pump, not shown.

Threaded, as at I9, on the outer end of the body member 4 is a thimble 20 which is formed axially and longitudinally with an internally threaded bore 2| for the reception of a needlecarrying thumb screw 22. The outer end of'this screw is headed as at 23 and disposed beyond the thimble 20 where it is readily accessible for manual adjustment. The screw 22' carries a fine needle rod 24 which extends through an axial passage formed in the screw 22 and is held in connection therewith by one or more transverse set screws shown at 25, and which pass through the screw head 23. The rod 24 projects longitudinally and axially beyond the inner end-of the change the rods or needles 2,4-to vary-their diameters, without breaking the partialvacuum which. exists within the apparatus.

The feathered or countersunk end ll of the passage I5, aided by high gas velocities within the- I passage, serve to minimize back diffusion and to give satisfactory linear results. In addition, the. time lag of the instrument by this construction is educedzto less thanone hundredth (.01), part of;a-. second. The gas samples handled by-the-apparatus-are. thus obtained while the subjectisnormally. breathing through an ordinary rubber mouthpiece of the type shown at 21. The breath passing through the outlet passage; 28 of the mouthpiece is introduced in part into a -hypodermic needle 29.,insertedthrough the walls of the rubber mouthpiece, the other. end of theneedle beingconnectedwith the tube 2; Thus breathing on thepart of the patient is not restricted and excitement is. avoided during the making: ofthe; test; I

The gas-samples which pass throu h the needle valve,- orif ce enter a conventional ionizing head-3i} arranged within the upper end of; the tube T. Within-thehead 30, the gasis subjected; as usual, toelectron bombardment. Thesions'iormed by this bombardment find no field with-in the ;head

but as they diiiuse in the form of a beam; through 1 asmall slitfillc in the bottom 33b of the;head, they are subjected to an acceleration potential of about 1509 volts, collimated by slits in other plates 3] and projected through the vacuumized tube into a neck SZ which is surrounded by a permanent or electromagnetfii- In thema-gnetic field produced;

bythemagnet 33, the; ion beams emanating from;

the head 30 are resolved, the ionized particles of lighter weight or low mass being diverted by-the magnetic field to a greater extentthan those; ff heavier weight or greater massso that the ions of the different gasesof the mixtureundergoing analysis are-separately'and individuallydeposited on the spaced collector plates indicated att l.v 35 and as-aiter passing through restricted slits SEa. Eachoithe collectorplatesis connected in a conventional-manner to the grldpf an electrometer tube 3]. Theintensity of the ion currents .falling uponthecollector platesli, 35 and 36 is measured by galvanometers, indicated at. arranged in theoutp ut circuits of a D. C. amplifier 39, the. latterbeing connectedin any conventional manner to the electronic tubes .31.

The electrons in. theionizing region of the head 3llmay be obtained from an electrically, heated tungsten filament shown at 40, accelerated acrossthetubethrough the head and collected by a trap 4| on theother side oithehead. The mag minefie n e ne k i re er Pr duced by e ma en ma n h. 0 e ss. field t ength. hei n col t ar ischareed by h ect on urre rou h i me-r s a ce providedin the amplifier 3 9.

asters iv t dand ire tedlu n; c e: pi turef lms rip. 43. e .i a -.m. tamera;

Thus with the apparatus comprising the present invention, the three main components of the breath are recorded continuously and simultaneously, so that changes in concentrationiof; any of the three can be determined with respect to the others so far as a given time base is concerned. Three identical amplifiers are employed with three collector systems and the output of each recordedby-means of mirror-type galvanometers on a common film strip. The great advantage of suchan instrument in any type of lung disorder is obvious, However, I do not limit the use of my apparatus to such a specific field but reserve the right; to. employ the same in all such fields to which it is adapted and of advantage.

I claim:

1 In. apparatus: for. analyzing a mixtura of. gases; a: massspectrometer having an ionization. chamber. and. a, gas sample-receiving. chamber; a. nozzleextending; into, said sample-receiving, chamber. and formed with a. restricted passage. communicating at one end with said; ionization chamber and terminating at its opposite end inan outwardly flaring funnel-shaped inlet. opening intosaidsample-receiving chamber; av valve stem arranged in longitudinal alignment with the inlet. opening of said nozzle and movable to regulate-the rate-of flow of gas from said sample-receiving chamber to said ionization chamber;. and'means for-establishing a positive flow of gas tobe analyzedthrough said sample-receivingchamberand in and around said nozzle.

2. In a mass spectrometer; a casingstructure including a head and an internal ionization chamber;a nozzle extending from said'head and form-,- ed wit-h a fine axially andlongitudinally disposedi gas passageterminating atthe outer end of saidnozzle in an enlarged funnel-shaped inlet opening and communicatingat its opposite end with said ionization chamber; a separate casing member connected withsaidheadin coaxial relation to saidnozzle, said separate casingv member being formed with an internal sample-receivingchamher into which the nozzle of said, headprojects; a threaded member carried by said separate, casing member; a longitudinally extendingneedle. valve joined with said threaded member, saidvalve beingmovable axially ofthe finepassageof. said, nozzle upon adjustment of a said threaded. member to control the flowof gasfromthe same pie-receiving chamber of said, separate. casing. member throughthe fine passage of saidnozzle and into the ionization chamber of said spectromeeter; andmeans for efiecting, a forced passage of gas to be tested by,the spectrometer through said sample receiving chamber in adirectionso, thata portion of the total quantity of the gas in: troduced into said sample-receiving chamber may be directed through the inlet opening of said ,nozzleand into said'ionization chamber.

REFERENCES CITED;

The following. referermes arev ,of record, in; the; fileoffi s pat nt:

N TED; STATES EA' TEN'ZCS" Number Name Date 2,310,435 Jenkins Feb-9,1943 2341.551 Hoover Feb.-15 1944 2,355,658.: Lawlor Aug-.- 15 1944 2380;082;v Sloan July-10; 1945 238054392 Hoskins et al Ju1y='31; 1945'' 2,387,786 Washburn Oct. 30. 1945 2;449;067 Guill'emin Sept. 14, 1948 

